Closed Loop Control Part A Flashcards
In a P-only controller, what 2 factors make up the dynamic gain?
1) Proportional gain of the controller
2) Dynamic gain of the process
What 3 responses can a feedback control loop in automatic have?
1) Sustained oscillations
2) Unstable response
3) Stable response
What 2 conditions are present when sustained oscillations?
1) Dynamic gain of the control loop is 1
2) 180 degree phase shift
What 2 conditions are present when the loop shows a stable response?
1) Dynamic gain is less than 1
2) less than180 degree phase shift
What 2 conditions are present when the loop shows an unstable response?
1) Dynamic gain is greater than 1
2) 180 degree phase shift
For a first order process, if the frequency increases, what happens to the dynamic gain and phase angle?
Dynamic gain: decreases
Phase angle: can increase up to 90 degrees
What is an example of a first order system?
1) Pressure of a vessel
2) Temperature control on a steam heat exchanger
For an integrating process, if the frequency increases, what happens to the dynamic gain and phase angle?
Dynamic gain: decreases
Phase angle: stays at 90 degrees
What component of the input signal affects the dynamic gain of an open loop system?
The amplitude or magnitude of the input signal
What does the Laplace transfer function define?
Laplace transfer function defines how a system’s output will behave after a change in input using frequency domain
What is an example of a multi capacity process?
Temperature in a distillation tower
What is an example of a deadtime process?
Conveyor belt
What effect does the addition of integral action have on a closed loop response of a multi capacity process?
Adding an integral action:
1) Decreases/eliminates offset
2) Decreases the stability as the loop can now show a damped or an unstable response
